The antinatriuretic and kaliuretic renal components of the physiological response to aldosterone have been demonstrated to be separable effects, possibly regulated by distinct and separate sets of biochemical events. We have suggested that hepatic metabolism of aldosterone to its polar and to its reduced metabolites is important in the mechanism of the action of this hormone. Synthesis of aldosterone metabolites in the liver may: (a) account for part of the latent period of aldosterone and (b) be necessary to maintain appropriate levels of these metabolites in the plasma and kidney, to mediate or regulate the individual renal electrolyte effects. Our obective is to continue the isolation and identification of each of the polar metabolites of aldosterone synthesized in the liver of male and female rats to determine their mineralocorticoid activity. The polar metabolites of aldosterone (NEPD) will be isolated in vivo from the liver, kidney and plasma, and from in vitro preparations of the liver of adrenalectomized and intact rats. These methods will provide sufficient quantities of these metabolites for chemical identification using GC-Mass Spec. analysis and for their biological testing. It will also be determined if the kidney can synthesize or further metabolize the metabolites of aldosterone synthesized in the liver. Each of the polar metabolites of aldosterone will be tested in vivo for their antinatriuretic and/or kaliuretic renal effects after administering them both subcutaneously and by infusion. We will also determine if these metabolites enhance or antagonize the mineralocorticoid activity of aldosterone. The reduced metabolites of aldosterone, which have been shown to be partial mineralocorticoid antagonists, will also be tested in this way to determine their biological relevance. The chemical structure and mineralcorticoid activity of the polar metabolites of aldosterone synthesized by the liver of hypertensive rats will also be examined. The effects of inducers and inhibitors of the cytochrome P-450 system on the hepatic synthesis of the individual metabolites of aldosterone will be investigated. These experiments will enable us to determine further the physiological importance of the hepatic metabolism of aldosterone.